DESCRIPTION (Applicant's Description): This is a competitive renewal of a training grant proposal for a program designed to train radiation biologists who will have knowledge of the molecular, cellular and tissue effects of radiation. Six predoctoral and 6 postdoctoral trainees are requested. Training will be offered in the radiation biology laboratories of the Division of Oncology Research, Department of Radiation Oncology at the University of Pennsylvania School of Medicine. The program will involve formal coursework, a lecture series and a journal club designed for the training needs of the applicants, research seminars and conferences, and laboratory research projects to be supervised by established investigators. The research projects will focus on various aspects of the currently funded research areas in the participating laboratories; for research projects, trainees will utilize techniques developed in modern biology to perform mechanistically-oriented studies in radiation biology/oncology. The research areas in which the 10 training directors and supervisors are involved are broadly based in cancer research, including molecular mechanisms in carcinogenesis and mutagenesis, molecular and cellular radiation biology, radiation chemistry and biochemistry, DNA repair processes, cancer prevention and radiation oncology. It is expected that graduates of the training program will continue with their research and academic careers in radiation biology and oncology.